J. Am. Chem. SOC.1994, 116, 4135-4136
New Ring-Containing Fluoropolymersf
4135
Table 1"
Zhen-Yu Yang,' Andrew E. Feiring, and Bruce E. Smart DuPont Central Research and Development Experimental Station, P.O.Box 80328 Wilmington, Delaware 19880-0328 Received January 31, 1994
Perfluoroplymers have excellent thermal and chemical stability, high insulating ability, and low refractive index and dielectric constant, but their limited solubility and high crystallinity necessitate extreme processing c0nditions.l Recently, ringcontaining polymers Teflon-AF* and Cytop3 were introduced by DuPont4 and Asahi Glass,5 respectively. In contrast to poly(tetrafluoroethylene), these cyclic fluoropolymers are amorphous but soluble only in selected fluorinated solvents.
comonomer
incorp(%)
M,
none TFEC CTFE PPVEd PSEPVEe
0 52.3 52 12 5.6
404000 84300 229000 71 200 118000
Mn
T,
Tm
190000 126.9 347 57 100 108000 18 100 19000
85 no 105.7 no 100.7 301.4 111.2 288.2
TGAb 485 480 440 470 440
a Polymerizations were carried out neat overnight. 10% weight loss under N2 when heated at 20 deg/min. Reaction in CFzCICFCIz a t 38 PSEPVE = CFz=CFOCFz"C for 8 h. PPVE = n-C,F,OCF=CF2. CF(CF3)0CF2CF2S02F.
which was dissolved in ethyl acetate and then reprecipitated by addition of methanol. The yield of polymer is greater than 90%.*
-
CFz=CFCF~CHzOCF=CFz
3
40°C
4
-cF$
Teflon@-AF
-
F- CFCFp
CYW@ 2
1
We now report that the partially fluorinated diene 3 undergoes a facile cyclopolymerization to afford a novel ring-containing fluoropolymer 4.6 The presence of only two hydrogens in the repeat unit of 4 results in remarkable changes in its solubility behavior and morphology as compared to its perfluorinated analog. Monomer 3' was prepared from 1,2-dichloroiodotrifluoroethane by the sequence shown in Scheme 1.
Scheme la CFpClCFClI
+
CFp=CFp
p,CF2CICFCICF2CF21
CFpClCFClCFpCOF
C
b
CFpCICFCICFpCHpOH
CFpCIC FCICFpCHpOCF=CFp
e
d
CFp=CFCFpCHpOCF=C
Fp
3
Reaction conditions: (a) ( P h C 0 0 ) ~(initiator), 135 "C, 55%; (b) 30% oleum, H g O (catalyst), 110 "C, 87%; (c) LiAlH4, 90%; (d) N a H ; CFz=CFz, 50 "C, 55%; (e) Zn,90 "C, 65%.
The polymerization of 3 can be carried out neat or in solution. Suitable free-radical initiators include bis(perfluoropropiony1) peroxide (3-P) and bis(4-tert- butylcyclohexylperoxy) dicarbonate. For example, when the monomer was mixed with 1 mol %of 3-P, sealed, and kept at 40-45 OC overnight, white solid was observed,
Unlike any other highly fluorinated polymer, 4 is soluble in polar aprotic solvents such as DMF, THF, glyme, acetone, and acetonitrile. It is insoluble in benzene, chloroform, 1,2,2trichlorotrifluoroethane, perfluorocarbons, and methanol, however. The high solubility indicates that the polymer is not crosslinked.9 The inherent viscosity of this polymer in D M F at 25 OC is 0.945 dL/g, and its refractive index is 1.394. GPC analysis (relative to polystyene as standard) indicates M , = 4.04 X 10s with M,/M,, = 2.12. Thermal gravimetric analysis of the homopolymer shows a high degree of thermal stability under nitrogen. Mass loss begins at 420 OC, with a 10% weight loss temperature of 485 "C. However, the stability of 4 significantly decreases in air (10% weight loss at 360 "C), presumably due to oxidation of carbonhydrogen bonds in the polymer. The polymer has a glass transition temperature of 127 OC by differential scanning calorimetry (DSC) and shows a melting point at 347 O C . The powder X-ray diffraction further confirms that the polymer is semicrystalline,lO in contrast to its perfluorinated counterpart 2. Monomer 3 readily copolymerizes with other fluorinated monomers, such as tetrafluoroethylene (TFE), chlorotrifluoroethylene (CTFE), and perfluorovinyl ethers. The results are summarized in Table 1. The copolymers, even those containing up to 52 mol %of TFE or CTFE, surprisingly retain good solubility in polar organic solvents, so colorless and transparent thin films can be readily cast from solution. All copolymers show good thermal stability with 10% mass loss above 440 O C in nitrogen. The trifluorovinyl ether copolymers are still partially crystalline, but, as expected, Tgand T, are lower than those of the homopolymer. By contrast, the copolymers containing relatively large amounts of TFE or CTFE are amorphous, with no melting points by DSC. Film X-ray diffraction further confirms that they are amorphous polymers. 11
Contribution no. 6794. (1) (a) Fluoropolymers; Wall, L. A. Ed.; John Wiley & Sons, Inc.: New York, 1972; Vol. XXV. (b) Carlson, D. P.; Schmiegel, W. Ullmann's (8) Anal. Calcd for ( C ~ H Z F ~ OC,) ~29.75; : H, 0.83; F, 62.79. Found: C, Encyclopedia of Industrial Chemistry; VCH Publishers: New York, 1988; 29.14; H, 0.93; F, 61.68. Vol. A1 1, p 393. (9) The IR spectrum shows no absorption at around 1790 cm-l which could (2) DuPont registered trademark. be attributed to residual double bonds. The I9F NMR spectrum indicated no (3) Asahi Glass registered trademark. vinylic fluorines. Peaks for saturated fluorines are shown at -1 12.5 to -122.0 (4) Resnick, P. R. Polym. Prepr., Am. Chem. Chem. Soc. Diu. Polym. and at -176.0 to -187.0 ppm in a 7:l ratio. The latter peaks are assigned to Chem. 1990, 31, 312. the fluorine on tertiary carbon and can be further considered as two sets of ( 5 ) Nakamura, N.; Kawasaki, T.; Unoki, M.; Oharu, K.; Sugiyama, N.; broad peaks at -176.0 to -179.0 and at -183.0 to -187.0 ppm in a 2:l ratio, Kaneko, I.; Kojima, G. Preprints of the First Pacific Polymer Conference, suggesting the existence of cis and trans isomers in a ratio of 2 1 . This cyclic Maui, HI, Dec, 1989; p 369. structure is further confirmed by 13C(l9F)NMR analysis. Peaks at 121.05, (6) Feiring,A. E.;Smart, B. E.;Yang,Z.-Y. U.S.Patent 5,260,492, (1993). 114.49, and 112.78 ppm correspond to the carbons of three CF2, and two sets of triplets at 73.40 ppm are assigned to CH2 carbon. Two tertiary carbons are (7) 'H NMR (CDCI3): 6 4.32 (t, J = 11.3 Hz). '9F NMR (CDCI3): 6 - 9 1 . 9 ( d d t 9 J = 5 7 . 7 H z , J = 3 6 . 6 H z , J = 5 . 4 H z lF),-l07.9(ddt,J= , 115.7 observed at 114.57 and 96.55 ppm, respectively. H z , J = 5 7 . 8 H z , J = 3 1 . 1 Hz,lF),-111.3(m,2F),-121.5(dd,J=99.4 (10) X-ray diffraction exhibited two type patterns: one with relative sharp H~,J~59.0H~,1F),-127.8(dd,J~109.0H~,J~99.5H~,1F),-137.4 peaks at 28 = 14.635" ( d = 6.050 29 A) and 17.395" ( d = 5.0982 A) and another with broad peaks at 28 = 30.142' ( d = 2.9649 A) and 38.202" ( d (dd, J = 109.0 Hz, J = 59.0 Hz, lF), -190.2 (ddt, J 115.5 Hz, J = 36.7 = -. 2 3559. . A1 Hz, J = 14.7 Hz, 1F). IR (neat): Y 2980 (w), 1845 (w), 1790 (vs), 1320 (m), . 1175 (vs), 1040 (v). Anal. Calcd for C ~ H ~ F S O C,: 29.75; H, 0.83. Found: (1 1) X-riy diffration for CTFE copolymer shows a broad amorphous peak C, 30.15; H, 0.85. at 28 = 15.395 ( d = 5.7557 A).
0002-7863/94/1516-4135$04.50/0
0 1994 American Chemical Society
4136 J . Am. Chem. SOC.,Vol. 116, No. 9, 1994 In conclusion, we have synthesized a new hydrofluoroalkenyl vinyl ether which readily homo- or copolymerizs to give ringcontaining fluoropolymers. The new polymers show remarkable solubility,l2 high thermal stability, and excellent optical clarity,
Communications to the Editor
which may lead to many potential applications. investigation is underway.
Further
Acknowledgment. We wish to acknowledge F. Davidson for
'3CNMR analysis, H. Williams for thermal analysis, and Dr.
M. H. Hung for insightful discussions. (12) The reason for this unprecedented solubility is not entirely clear, although there is accumulating evidence that the hydrogens in a -CFzCHzSupplementaryMaterial Available: Experimental details and ORFunit have peculiarly strong hydrogen-bonding capabilities. For example, the methylene IH chemical shifts in [CF~CFH~CF~CF(CF~)OCFZCFZCH~O]. characterization data for monomer 3 and homopolymer (4 pages). polyethers range from 3.77 ppm in C6D6 to 4.69 ppm in and This material is contained in many libraries on microfiche, certain related cyclic ethers actually form stable hydrogen-bonded complexes immediately follows this article in the microfilm version of the with fluoride ions." Notably, the solubility character of the isomeric polymer 5 is very similar to that for 2 but entirely different from that for 4.15 journal, and can be ordered from the ACS; see any current ~~
~
~
masthead page for ordering information. (13) Hung, M.-H.; Farnham, W. B.; Feiring, A. E.; Rozen, S. J. Am.
5
Chem. SOC.1993, 115, 8954. (14) Farnham, W. B.; Roe, D. C.; Dixon, D. A.; Calabrese, J. C.; Harlow, R. L.J. Am. Chem. Soc. 1990, 112, 7707. (15) Inukai, H. Japanese Patent 91 JP-234319, 1993.
